Re: [PATCH RFC 0/2] Packed ring for vhost

[Jason Wang]

On 2018å02æ14æ 10:47, Michael S. Tsirkin wrote:
> On Wed, Feb 14, 2018 at 10:37:07AM +0800, Jason Wang wrote:
> > Hi all:
> >
> > This RFC implement a subset of packed ring which was described at
> > https://github.com/oasis-tcs/virtio-docs/blob/master/virtio-v1.1-packed-wd07.pdf
> > . The code were tested with pmd implement by Jens at
> > http://dpdk.org/ml/archives/dev/2018-January/089417.html. Minor
> > change was needed for pmd codes to kick virtqueue since it assumes a
> > busy polling backend.
> >
> > Test were done between localhost and guest. Testpmd (rxonly) in guest
> > reports 2.4Mpps. Testpmd (txonly) repots about 2.1Mpps.
> How does this compare with the split ring design?

No obvious difference (+-5%). I believe we reach the bottleneck of vhost.

> > It's not a complete implemention, here's what were missed:
> >
> > - Device Area
> > - Driver Area
> > - Descriptor indirection
> > - Zerocopy may not be functional
> > - Migration path is not tested
> > - Vhost devices except for net
> > - vIOMMU can not work (mainly because the metadata prefetch is not
> >    implemented).
> > - See FIXME/TODO in the codes for more details
> > - No batching or other optimizations were implemented
> ioeventfd for PIO/mmio/s390.

Probably, but this is not the stuffs of packed ring I think.

Thanks